[package.proto] convert deps from list to map.

unittests/test_test.py

 #!/usr/bin/env python
 # Copyright 2017 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import json
 import os
 import shutil
 import subprocess
 import sys
@@ skipping 197 matching lines @@
     os.makedirs(config_dir)
 
     self._root_dir = root_dir
     self._recipes_cfg = os.path.join(config_dir, 'recipes.cfg')
     self._recipe_tool = os.path.join(ROOT_DIR, 'recipes.py')
 
     test_pkg = package_pb2.Package(
         api_version=1,
         project_id='test_pkg',
         recipes_path='',
-        deps=[
-            package_pb2.DepSpec(
-                project_id='recipe_engine',
-                url='file://'+ROOT_DIR),
-        ],
+        deps={
+          'recipe_engine': package_pb2.DepSpec(url='file://'+ROOT_DIR),
+        }
     )
     package.ProtoFile(self._recipes_cfg).write(test_pkg)
 
     self.maxDiff = None
 
   def tearDown(self):
     shutil.rmtree(self._root_dir)
 
   @property
   def json_path(self):
@@ skipping 570 matching lines @@
     rw.RunStepsLines = ['pass']
     rw.GenTestsLines = ['yield api.test(%r)' % test_name]
     rw.add_expectation(test_name)
     rw.write()
     self._run_recipes('test', 'run', '--json', self.json_path)
     self.assertEqual(self.json_generator.get(), self.json_contents)
 
 
 if __name__ == '__main__':
   sys.exit(unittest.main())